Known wireless power supply techniques include a power supply using electromagnetic induction, and a power supply using radiowaves. In the meantime, a power supply using magnetic resonance has been proposed in recent years.
With the wireless supply method using magnetic resonance, for example, a resonance coil having a certain resonance frequency is arranged in a power transmission device, and a resonance coil having the same resonance frequency as that of the power transmission device is arranged in a power reception device. Magnetic field coupling that enables an electromagnetic energy transfer is caused by magnetic resonance between the power transmission device and the power reception device, so that power is efficiently transmitted from the resonance coil of the power transmission device to that of the power reception device with the magnetic field coupling.
With the power supply method using magnetic resonance, power higher than that with the power supply method using radiowaves can be supplied, and a power transmission distance can be prolonged or a power transmission coil can be reduced in size in comparison with that of the power supply method using electromagnetic induction.
A certain known cellular phone includes a main antenna for a communication, which is connected to a wireless unit within a housing and intended to make a communication with radiowaves, and loop-shaped electromagnetic antennas each of which is connected to an IC module within the housing and intended to contactlessly transmit/receive data between an external device and the IC module with electromagnetic induction. In the cellular phone, the loop-shaped electromagnetic antennas are arranged on a back surface provided with a battery cover and a side surface of the housing. Thus, the cellular phone can contactlessly transmit/receive various types of data to/from an external device on both a front surface side and the back surface side.
A certain known cordless telephone device includes a handset, and a charging unit on which the handset is placed selectively by normally orientating a key operation part downward or by turning over the key operation part upward. The charging unit includes an oscillator circuit, and a primary coil connected to the oscillator circuit. The handset includes a battery for a power source, a secondary coil for generating an alternating current with electromagnetic induction by AC-oscillating the primary coil in a state where the handset is placed on the charging unit, and a rectifying smoothing circuit for supplying an output of the secondary coil to the battery. In a concave portion of the charging unit, on which the handset is placed, at least two pairs of protrusions for supporting the handset are provided. The cordless telephone device has a bottom surface that is provided on a side opposite to the key operation unit of the handset and separates a speaker for amplifying voice when the handset is placed via at least the two pairs of protrusions by being turned over.
A certain known portable communication device has a cover rotatable about an axis part. The portable communication device also includes a unit to be charged, which includes a power reception coil core around which a power reception coil is wound, and a secondary battery, and forms a main body of the portable communication device, and a charging unit having a power transmission coil core around which a power transmission coil is wound. The power reception coil core is formed in the shape of a bar, and included in an axis part of the unit to be charged in the main body of the portable communication device. Moreover, part of the power transmission coil core faces both ends of the power reception coil core formed in the shape of the bar in a state where the unit to be charged is placed on the charging unit. Thus, a contactless power transmission efficiency using electromagnetic induction between the coils of the charging unit and the unit to be charged can be increased regardless of the shape of the bottom part of the main body of the portable communication device.    Patent Document 1: Japanese Laid-Open Patent Publication No. 2005-333244    Patent Document 2: U.S. Pat. No. 3,514,519 (Japanese Laid-Open Patent Publication No. HEI8-46671)    Patent Document 3: Japanese Laid-Open Patent Publication No. HEI10-4639